Method of manufacturing multi-color light emitting pixel unit

ABSTRACT

A method for fabricating a multi-color light emitting pixel unit, includes: forming a stack structure on a substrate, the stack structure comprising a first metal layer, a first type of light emitting layer, a second metal layer, and a second type of light emitting layer in an order from bottom to top; patterning the second type of light emitting layer and the second metal layer until a portion of the first type of light emitting layer is exposed; and selectively etching the stack structure to form a first light emitting transistor and a second light emitting transistor, the first light emitting transistor including the first metal layer and the first type of light emitting layer, and the second light emitting transistor including the first metal layer, the first type of light emitting layer, the second metal layer, and the second type of light emitting layer.

FIELD OF THE INVENTION

The present disclosure generally relates to semiconductor manufacturingtechnology field and, more particularly, to a method of manufacturing amulti-color light emitting pixel unit.

BACKGROUND OF THE INVENTION

With the requirement for miniaturization and portability of electronicdevices, it is increasingly important for a light emitting device tointegrate a plurality of various types of light emitting transistors andmulti-color light emitting pixel units. A conventional process offabricating a multi-color display chip includes forming a first type oflight emitting region and then forming another type of light emittingregion. The conventional process of fabricating the different types oflight emitting regions becomes increasingly difficult, due to thecomplexity of aligning processes and transferring processes, etc.,thereby leading to problems such as decreased alignment accuracy,decreased yield, and increased cost, etc.

In addition, the conventional process of fabricating various lightemitting regions usually includes: bonding a base having an epitaxiallayer to a substrate, and then peeling off the base, which causes stressin the epitaxial layer, which may result in warpage and deformation ofthe epitaxial layer. In addition, the current light emitting displaychip integrating different types of light emitting regions further hasproblems such as high power consumption and heat dissipation.

BRIEF SUMMARY OF THE DISCLOSURE

According to one aspect of the present disclosure, a method forfabricating a multi-color light emitting pixel unit is provided. Themethod includes: forming a stack structure on a substrate, the stackstructure comprising a first metal layer, a first type of light emittinglayer, a second metal layer, and a second type of light emitting layerin an order from bottom to top; patterning the second type of lightemitting layer and the second metal layer until a portion of the firsttype of light emitting layer is exposed; and selectively etching thestack structure to form a first light emitting transistor and a secondlight emitting transistor, the first light emitting transistor includingthe first metal layer and the first type of light emitting layer, andthe second light emitting transistor including the first metal layer,the first type of light emitting layer, the second metal layer, and thesecond type of light emitting layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a multi-color lightemitting pixel unit according to an embodiment of the presentdisclosure.

FIG. 2 is a cross-sectional view illustrating a multi-color lightemitting pixel unit according to an embodiment of the presentdisclosure.

FIG. 3 is a cross-sectional view illustrating a multi-color lightemitting pixel unit according to an embodiment of the presentdisclosure.

FIG. 4 is a top view illustrating a multi-color light emitting pixelunit according to an embodiment of the present disclosure.

FIG. 5 is a cross-sectional view illustrating a multi-color lightemitting pixel unit according to an embodiment of the presentdisclosure.

FIG. 6 is a flow chart illustrating a method of fabricating themulti-color light emitting pixel unit illustrated in FIG. 1, accordingto an embodiment of the present disclosure.

FIGS. 7 to 10 are cross-sectional views illustrating structures formedin the steps of the method in FIG. 6, according to an embodiment of thepresent disclosure.

FIG. 11 is a flow chart illustrating details of step S601 in FIG. 6,according to an embodiment of the present disclosure.

FIGS. 12 to 21 are cross-sectional views illustrating structures formedin the steps in FIG. 11, according to an embodiment of the presentdisclosure.

FIG. 22 is a flow chart illustrating details of step S604 in FIG. 6,according to an embodiment of the present disclosure.

FIGS. 23 to 25 are cross-sectional views illustrating structures formedin the steps in FIG. 22, according to an embodiment of the presentdisclosure.

FIGS. 26 and 27 are cross-sectional views illustrating structures formedduring a process of fabricating a first electrical connector, accordingto an embodiment of the present disclosure.

FIG. 28 is a cross-sectional view illustrating a multi-color lightemitting pixel unit having micro-gap structures, according to anembodiment of the present disclosure.

FIG. 29 is a flow chart illustrating a method of fabricating themulti-color light emitting pixel unit illustrated in FIG. 3, accordingto an embodiment of the present disclosure.

FIGS. 30 to 34 are cross-sectional views illustrating structures formedin the steps of the method in FIG. 29, according to an embodiment of thepresent disclosure.

FIG. 35 is a flow chart illustrating details of step S701 in FIG. 29,according to an embodiment of the present disclosure.

FIG. 36 is a cross-sectional view of micro-gap structures formed inthree types of light emitting layers, according to an embodiment of thepresent disclosure.

FIG. 37 is a flow chart illustrating details of step S705 in FIG. 29,according to an embodiment of the present disclosure.

FIGS. 38 to 40 are cross-sectional views illustrating the structuresformed in the steps in FIG. 37, according to an embodiment of thepresent disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments to provide a further understanding of the disclosure. Thespecific embodiments and the accompanying drawings discussed are merelyillustrative of specific ways to make and use the disclosure, and do notlimit the scope of the disclosure or the appended claims.

Hereinafter combined with FIGS. 1 to 40, the present disclosure isfurther described by the embodiments of the disclosure. It should bepointed out that all appended drawings adopt a very simplified form andimprecise scaling is merely used to assistant explain the embodiments ofthe disclosure conveniently and clearly.

A multi-color light emitting pixel unit disclosed herein at leastincludes one type of light emitting transistor, or several types oflight emitting transistors. Each type of light emitting transistorincludes an upper conductive layer, a bottom conductive layer, and alight emitting layer between the upper conductive layer and the bottomconductive layer. All of the light emitting transistors share the sameupper conductive layer and the same bottom conductive layer. It shouldbe noted that, the light emitting layer can be a single layer ormultiple layers. A middle layer can be arranged between two of multiplelight emitting layers in a same light emitting diode. It is assumed thata multi-color light emitting pixel unit includes first to Mth types oflight emitting transistors, where M is an integer and not less than two.Each one of the first to Mth types of light emitting transistors atleast includes a same type of light emitting layer. For example, eachone of the first to Mth types of light emitting transistors includes afirst type of light emitting layer. Any one of the second type to Mthtype of light emitting layers is different from the first type of lightemitting layer. A micro display panel including a plurality of the pixelunits mentioned above arranged in a matrix is also provided in thepresent disclosure.

In some embodiments, the light emitting transistor can be at least oneof a light emitting diode (LED), a Schottky light emitting transistor,and etc. The top conductive layer of the light emitting transistor is,but not limited to, a transparent conductive layer, and the bottomconductive layer of the light emitting transistor is, but not limitedto, a metal layer. Hereinafter, the LED is used as an example of thelight emitting transistor, but this does not limit the scope of thepresent disclosure. A person skilled in the art can change the LED toanother light emitting transistor according to conventional technicalmeans.

FIG. 1 is a cross-sectional view illustrating a multi-color lightemitting pixel unit 1000, according to an embodiment of the presentdisclosure. Referring to FIG. 1, the multi-color light emitting pixelunit 1000 includes, at least, a first type of LED 01 and a second typeof LED 02 arranged side by side on a substrate 100. The top of the firsttype of LED 01 and the top of the second type of LED 02 are not at asame horizontal plane. The type of the first type of LED 01 is differentfrom that of the second type of LED 02. Herein, as shown in FIG. 1, thetop of the first type of LED 01 is lower than that of the second type ofLED 02. According to an embodiment, the first type of LED 01 is selectedfrom one of a red LED, a green LED, a blue LED, a yellow LED, an orangeLED, or a cyan LED, and the second type of LED 02 is selected from oneof a green LED, a blue LED, a red LED, a yellow LED, an orange LED, or acyan LED. Additionally, the size of a light emitting area of the firsttype of LED 01 is different from that of the second type of LED 02. Forexample, the first type of LED 01 is a red LED, the second type of LED02 is a green LED, and the size of the light emitting area of the redLED is different from that of the green LED. Furthermore, according todifferent color that may be needed, the light emitting area of the greenLED can be smaller than that of the red LED.

In addition, an isolation structure 07 is arranged between the firsttype of LED and the second type of LED. In the embodiment illustrated inFIG. 1, the isolation structure 07 between the first type of LED 01 andthe second type of LED 02 is an isolation trench. The multi-color lightemitting pixel unit 1000 includes a first metal layer, a first type oflight emitting layer, a second metal layer, and a second type of lightemitting layer. As illustrated in FIG. 1, the first type of LED 01includes, at least, a first segment of a first metal layer 101-1 and afirst segment of a first type of light emitting layer 102-1 in an orderfrom bottom to top. The first segment of the first metal layer 101-1constitutes a bottom conductive layer of the first type of LED 01. Thesecond type of LED 02 includes, at least, a second segment of the firstmetal layer 101-2, a second segment of the first type of light emittinglayer 102-2, a first segment of a second metal layer 201-1, and a firstsegment of a second type of light emitting layer 202-2 in an order frombottom to top, and a first electrical connector 203. The first segmentof the first metal layer 101-1 and the second segment of the first metallayer 101-2 are electrically connected with the substrate 100. Theisolation structure 07 isolates the first segment of the first metallayer 101 1 in the first type of LED 01 from the second segment of thefirst metal layer 101-2 in the second type of LED 02. The isolationstructure 07 also isolates the first segment of the first type of lightemitting layer 102-1 in the first type of LED 01 from the second segmentof the first type of light emitting layer 102-2 in the second type ofLED 02. Additionally, in order to simplify the manufacturing process,the first segment of the second metal layer 201-1, the second segment ofthe first type of light emitting layer 102-2, and the second segment ofthe first metal layer 101-2 in the second type of LED 02 areelectrically connected with each other by the first electrical connector203. According to one embodiment, the first electrical connector 203 canbe attached to and contact part or all of the side wall surface of thesecond type of LED 02. Alternatively, the first electrical connector 203can be attached to and contact only the surface of the first segment ofthe second metal layer 201-1 and the second segment of the first metallayer 101-2 in the second type of LED 02. Still alternatively, the firstelectrical connector 203 can be formed as a conductive side arm attachedto and contacting the sidewalls of the first segment of the second metallayer 201-1, the second segment of the first type of light emittinglayer 102-2, and the second segment of the first metal layer 101-2. Theelectrical connector 203 between the second segment of the first metallayer 101-2 and the first segment of the second metal layer 201-1 in thesecond type of LED 02 can have another shape, such as a curved line. Inthe embodiment illustrated in FIG. 1, the first electrical connector 203is attached to the sidewall of the second type of LED 02, so that thefirst electrical connector 203 conforms to the surface topography of theside wall of the second type of LED 02.

Referring to FIG. 1, a top isolation layer 04 and a top transparentconductive layer 05 are arranged on the first segment of the first typeof light emitting layer 102-1 in the first type of LED 01 and the firstsegment of the second type of light emitting layer 202-1 in the secondtype of LED 02. The top isolation layer 04 covers the first segment ofthe first type of light emitting layer 102 1, the first segment of thesecond type of light emitting layer 202 1, and the exposed substrate100. The top isolation layer 04 has openings exposing portions of thetop surfaces of the first segment of the first type of light emittinglayer 102-1 and the first segment of the second type of light emittinglayer 202 1. The top transparent conductive layer 05 covers the topisolation layer 04 and is formed in the openings of the top isolationlayer 04, and thereby contacts the exposed top surfaces of the firstsegment of the first type of light emitting layer 102 1 and the firstsegment of the second type of light emitting layer 202-1 via theopenings.

The substrate 100 is an integrated circuit (IC) substrate. The ICsubstrate includes an interconnection layer, which is electricallyconnected with the first segment of the first metal layer 101-1 in thefirst type of LED 01 and the second segment of the first metal layer 1012 in the second type of LED 02. Since the first electrical connector 203is connected with the second segment of the first metal layer 101-2 inthe second type of LED 02, the first electrical connector 203 isconnected with the interconnection layer in the substrate 100. Inaddition, referring to FIG. 1, the bottom of the first electricalconnector 203 extends to the substrate 100 to connect with theinterconnection layer. Herein, the IC substrate at least includes adrive circuit. The drive circuit controls every LED separately.

FIG. 2 is a cross-sectional view illustrating a multi-color lightemitting pixel unit 2000, according to an embodiment of the presentdisclosure. Referring to FIG. 2, the multi-color light emitting pixelunit 2000 includes, at least, the first type of LED 01, the second typeof LED 02, and a third type of LED 03, which are arranged on a samesubstrate 100. The third type of LED 03 is different from the first typeof LED 01 and the second type of LED 02. Herein, the first type of LED01 is selected from one of a red LED, a green LED, a blue LED, a yellowLED, am orange LED, or a cyan LED; the second type of LED 02 is selectedfrom one of a green LED, a blue LED, a red LED, a yellow LED, an orangeLED, or a cyan LED; and the third type of LED 03 is selected from one ofa blue LED, a red LED, a green LED, a yellow LED, an orange LED, or acyan LED. For example, a red LED is selected as the first type of LED01, a green LED is selected as the second type of LED 02, and a blue LEDis selected as the third type of LED 03. Referring to FIG. 2, the heightof the third type of LED 03 is different from that of the first type ofLED 01. Furthermore, the height of the first type of LED 01 is differentfrom that of the second type of LED 02, while the height of the secondtype of LED 02 is the same as that of the third type of LED 03. In otherembodiments, the height of the third type of LED 03, the height of thefirst type of LED 01, and the height of the second type of LED 02 can bedifferent from each other, as shown in FIG. 3.

In the multi-color light emitting pixel unit 2000, the structures of thefirst type of LED 01 and the second type of LED 02 are the same as thoseof the first type of LED 01 and the second type of LED 02 in themulti-color light emitting pixel unit 2000, and therefore detaileddescriptions thereof are not repeated. The third type of LED 03 in themulti-color light emitting pixel unit 2000 includes, at least, a thirdsegment of the first metal layer 101-3, a third segment of a first typeof light emitting layer 102-3, a first segment of a third metal layer301-1, and first segment of a third type of light emitting layer 302-1in an order from bottom to top, and a second electrical connector 303connecting the third segment of the first metal layer 101-3 and thefirst segment of the third metal layer 301-1. The multi-color lightemitting pixel unit 2000 also includes a top isolation layer 04 coveringthe first type of LED 01, the second type of LED 02, and the third typeof LED 03, and having opening exposing a portion of the first segment ofthe first type of light emitting layer 102-1 in the first type of LED01, a portion of the first segment of the second type of light emittinglayer 202-1, and a portion of the first segment of the third type oflight emitting layer 302-1. A top electrode layer 05 is formed on top ofthe top isolation layer 04 and contacts the first segment of the firsttype of light emitting layer 102-1, the first segment of the second typeof light emitting layer 202-1, and the first segment of the third typeof light emitting layer 302-1 via the openings of the top isolationlayer 04.

FIG. 3 is a cross-sectional view illustrating a multi-color lightemitting pixel unit 3000, according to an embodiment of the presentdisclosure. Referring to FIG. 3, in the multi-color light emitting pixelunit 3000, the top of the third type of LED 03 is higher than that ofthe second type of LED 02, while the height of the first type of LED isdifferent from that of the second type of LED 03.

FIG. 4 is a top view of the multi-color light emitting pixel unit 4000,according to an embodiment of the present disclosure. The multi-colorlight emitting pixel unit 4000 can be the multi-color light emittingpixel unit 2000 illustrated in FIG. 2 or the multi-color light emittingpixel unit 3000 illustrated in FIG. 3. FIG. 4 illustrates thearrangement of the three types of the LEDs 01, 02, and 03 in a pixelunit, but the present disclosure also includes other arrangements, suchas a matrix. Herein, the size of the light emitting area of the thirdtype of LED 03 is different from that of the first type of LED 01 and isdifferent from that of the second type of the LED 02. For example, thefirst type of LED 01 is a red LED, the second type of LED 02 is a greenLED, and the third type of LED 03 is blue LED. The size of the lightemitting area of each one of the first, second, and third type of LEDs01, 02, and 03 can be determined according to the required light colorto be emitted by the multi-color light emitting pixel unit 4000. Whenwhite light is required, the size of the light emitting area of the redLED is larger than that of the green LED, and the size of the lightemitting area of the blue LED is larger than that of the green LED. Asshown in FIG. 4, the space between the red LED and the blue LED islarger than the space between the blue LED and the green LED; the spacebetween the red LED and the green LED is larger than the space betweenthe blue LED and the green LED, so as to achieve a better light emissioneffect.

Referring back to FIG. 3, an isolation structure 07 is arranged betweentwo of the first type of LED 01, the second type of LED 02, and thethird type of LED 03. The isolation structure is an isolation trench.The first type of LED 01, the second type of LED 02, and the third typeof LED 03 are formed from a first metal layer 101, a first type of lightemitting layer 102, a second metal layer 201, a second type of lightemitting layer 202, a third metal layer 301, and a third type of lightemitting layer 302. The first type of LED 01 and the second type of LED02 in FIG. 3 are the same as the first type of LED 01 and the secondtype of LED 02 in FIG. 2. Specifically, as illustrated in FIG. 3, thefirst type of LED 01 includes, at least, a first segment of a firstmetal layer 101-1 and a first segment of a first type of light emittinglayer 102-1 in an order from bottom to top. The second type of LED 02includes, at least, a second segment of the first metal layer 101-2, asecond segment of the first type of light emitting layer 102-2, a firstsegment of a second metal layer 201-1, and a first segment of a secondtype of light emitting layer 202-1 in an order from bottom to top, and afirst electrical connector 203. The third type of LED 03 includes, atleast, a third segment of the first metal layer 101-3, a third segmentof the first type of light emitting layer 102-3, a second segment of thesecond metal layer 201-2, a second segment of the second type of lightemitting layer 202-2, a first segment of a third metal layer 301-1, anda first segment of a third type of light emitting layer 302-1 in anorder from bottom to top, and a second electrical connector 303. Asshown in FIG. 3, the first segment of the first metal layer 101-1, thesecond segment of the first metal layer 101-2, and the third segment ofthe first metal layer 101-3 are electrically connected with thesubstrate 100. The first electrical connector 203 in the second type ofLED 02 electrically connects the first segment of the second metal layer201-1 with the second segment of the first metal layer 101-2. The secondelectrical connector 303 in the third type of LED 03 electricallyconnects the first segment of the third metal layer 301-1 with thesecond segment of the second metal layer 201-2 and the third segment ofthe first metal layer 101-3. The isolation structure 07 isolates thefirst segment of the first metal layer 101-1 in the first type of LED 01from the second segment of the first metal layer 101-2 in the secondtype of LED 02 and the third segment of the first metal layer 101-3 inthe third type of LED 03, isolates the first segment of the first typeof light emitting layer 102-1 in the first type of LED 01 from thesecond segment of the first type of light emitting layer 102-2 in thesecond type of LED 02 and the third segment of the first type of lightemitting layer 102-3 in the third type of the LED 03, isolates the firstsegment of the second metal layer 201-1 in the second type of LED 02from the second segment of the second metal layer 201-2 in the thirdtype of LED 03, and isolates the first segment of the second type oflight emitting layer 202-1 in the second type of LED 02 from the secondsegment of the second type of light emitting layer 202-2 in the thirdtype of LED 03. It should be noted that, the first electrical connector203 is used to connect the second segment of the first type of lightemitting layer 102-2 with the second segment of the first metal layer101-2 in the second type of LED 02, while the second electricalconnector 303 is used to connect the second segment of the second typeof light emitting layer 202-2 and the third segment of the first type oflight emitting layer 102-3 with the third segment of the first metallayer 101-3 in the third type of LED 03. Thus, in order to simplify themanufacturing process, in the same manner as FIG. 1, the firstelectrical connector 203 further connects the second segment of firsttype of light emitting layer 102-2 with the second segment of the firstmetal layer 101-2. That is, in the second type of LED 02, the firstelectrical connector 203 connects the first segment of the second metallayer 201-1 and the second segment of the first type of light emittinglayer 102-2 with the second segment of the first metal layer 101-2. Thesecond electrical connector 303 further connects the second segment ofthe second type of light emitting layer 202-2 with the third segment ofthe first metal layer 101-3. That is, in the third type of LED 03, thesecond electrical connector 303 connects the first segment of the thirdmetal layer 301-1, the second segment of the second type of lightemitting layer 202-2, and the second segment of the second metal layer201-2 with the third segment of the first metal layer 101-3.Alternatively, the second electrical connector 303 further connects thesecond segment of the second type of light emitting layer 202-2 and thethird segment of the first type of light emitting layer 102-3 with thethird segment of the first metal layer 101-3. That is, in the third typeof LED 03, the second electrical connector 303 connects the firstsegment of the third metal layer 301-1, the second segment of the secondtype of light emitting layer 202-2, the second segment of the secondmetal layer 201-2, and the third segment of the first type of lightemitting layer 102-3 with the third segment of the first metal layer101-3. In addition, the bottom of the first electrical connector 203 andthe bottom of the second electrical connector 303 separately anddirectly contact the substrate 100, thereby simplifying themanufacturing process. It should be noted that the materials of thefirst electrical connector 203 and the second electrical connector 303are formed of conductive metals. In an embodiment, the second electricalconnector 303 is attached to and contacts the side wall surface of thethird type of LED 03.

In one embodiment, the first type of light emitting layer is a red lightemitting layer, the second type of light emitting layer is a green lightemitting layer, and the third type of light emitting layer is a bluelight emitting layer, the first type of LED 01 is a red LED 01, thesecond type of LED 02 is a green LED 02, and the third type of LED 03 isa blue LED 03. In the red LED 01, an electrical voltage applied betweenthe top transparent conductive layer 05 and the first segment of thefirst metal layer 101-1 is applied to the first segment of the red lightemitting layer 102-1. As a result, the first segment of the red lightemitting layer 102-1 in the red LED 01 emits red light. In the green LED02, the first electrical connector 203 electrically connects the secondsegment of the red light emitting layer 102-2 with the second segment ofthe first metal layer 101-2, such that an electrical voltage appliedbetween the top transparent conductive layer 05 and the second segmentof the first metal layer 101-2 is only applied to the first segment ofthe green light emitting layer 202-1. As a result, only the firstsegment of the green light emitting layer 202-1 in the green LED 02emits green light while the second segment of the red light emittinglayer 102-2 in the green LED 02 does not emit light. In the third typeof LED 03, the second electrical connector 303 electrically connects thethird segment of the red light emitting layer 102-3 and the secondsegment of the green light emitting layer 202-2 with the third segmentof the first metal layer 101-3, such that an electrical voltage appliedbetween the top transparent conductive layer 05 and the third segment ofthe first metal layer 101-3 is only applied to the first segment of theblue light emitting layer 302-1. As a result, only the first segment ofthe blue light emitting layer 302-1 in the blue LED 03 emits blue lightwhile the third segment of the red light emitting layer 102-3 and thesecond segment of the green light emitting layer 202-2 in the blue LED03 do not emit light.

Referring again to FIG. 3, a top isolation layer 04 and a toptransparent conductive layer 05 are arranged on the first type of LED01, the second type of LED 02, and the third type of LED 03. The topisolation layer 04 covers the first segment of the first type of lightemitting layer 102-1, the first segment of the second type of lightemitting layer 202-1, the first segment of the third type of lightemitting layer 302-1, and the exposed substrate 100. Openings arearranged in the top isolation layer 04 to expose portions of the topsurfaces of the first segment of the first type of light emitting layer102-1, the first segment of the second type of light emitting layer202-1, and the first segment of the third type of light emitting layer302-1. The top transparent conductive layer 05 covers the top isolationlayer 04 and is formed in the openings of the top isolation layer 04,thereby contacting the exposed top surface of the first segment of thefirst type of light emitting layer 102-1, the exposed top surface of thefirst segment of the second type of light emitting layer 202-1, and theexposed top surface of the first segment of the third type of lightemitting layer 302-1.

The detailed description of the substrate 100 in the multi-color lightemitting pixel unit 3000 with at least three types of LEDs correspondsto the description of FIG. 1 and will be not repeated herein. It shouldbe noted that, the interconnection layer in the IC substrate 100 iselectrically connected to the first type of LED 01, the second type ofLED 02, and the third type of LED 03. The driver circuit in the ICsubstrate 100 controls every LED separately.

In the multi-color light emitting pixel units 1000 to 4000 in FIGS. 1 to4, one or more of the emitting layers 102, 202, and 302 can havemicro-gap structures. For example, in the multi-color light emittingpixel unit 1000 shown in FIG. 1, the first type of light emitting layer102 can have micro-gap structures, or the second type of light emittinglayer 202 can have micro-gap structures, or both of the first type oflight emitting layer 102 and the second type of light emitting layer 202can have micro-gap structures. As another example, in the multi-colorlight emitting pixel unit 3000 shown in FIG. 3, the first type of lightemitting layer 102 can have micro-gap structures, or the second type oflight emitting layer 202 can have micro-gap structures, or the thirdtype of light emitting layer 302 can have micro-gap structures, or bothof the first type of light emitting layer 102 and the second type oflight emitting layer 202 can have micro-gap structures, or both of thesecond type of light emitting layer 202 and the third type of lightemitting layer 302 can have micro-gap structures, or both of the firsttype of light emitting layer 102 and the third type of light emittinglayer 302 can have micro-gap structures, or all of the first type oflight emitting layer 102, the second type of light emitting layer 202and the third type of light emitting layer 302 can have micro-gapstructures. Herein, each one of the micro-gap structures in themulti-color light emitting pixel units 1000 to 3000 illustrated in FIGS.1 to 3 can be, but are not limited to, an air gap. The air gap issealed. Preferably, the cross-sectional dimension of the air gap is notmore than 2 nm, so as to release the stress in the light emitting layerand avoid curving of the light emitting layer without impacting thelight emitting efficiency of the light emitting layer. Here, thecross-sectional dimension of the air gap can be the diameter of thecross section of the air gap, or the length or width of the crosssection of the air gap.

FIG. 5 is a cross-sectional view illustrating a multi-color lightemitting pixel unit 5000, according to an embodiment of the presentdisclosure. As shown in FIG. 5, each one of the first type of lightemitting layer 102, the second type of light emitting layer 202, and thethird type of light emitting layer 302 can have a plurality of micro-gapstructures 06. Each one of the micro-gap structures 06 extends along adirection perpendicular to the substrate 100, and penetrates thecorresponding light emitting layer, such as the first type of lightemitting layer 102, the second type of light emitting layer 202, or thethird type of light emitting layer 302. When multiple light emittinglayers are used in an embodiment, the micro-gap structure 06 is arrangedat least one light emitting layer, preferably in the top light emittinglayer.

Still referring to FIG. 5, the micro-gap structures 06 are staggered oneon another in the multiple light emitting layers. That is, the micro-gapstructures 06 in the first type of light emitting layer 102 are notvertically aligned with the micro-gap structures 06 in the second typeof light emitting layer 202, and the micro-gap structures 06 in thesecond type of light emitting layer 202 are not vertically aligned withthe micro-gap structures 06 in the third type of light emitting layer302. In each one of the second type of LED 02 and the third type of LED03, the micro-gap structures in the first type of light emitting layer102 is isolated and sealed between the second metal layer 201 at the topof the first type of light emitting layer 102 and the first metal layer101 at the bottom thereof. In the third type of LED 03, the micro-gapstructures 06 in the second type of light emitting layer 202 is isolatedand sealed between the third metal layer 301 at the top of the secondlight emitting layer 202 and the second metal layer 201 at the bottomthereof, and the micro-gap structures 06 in the third type of lightemitting layer 302 is isolated and sealed between the top isolationlayer 04 at the top of the third type of light emitting layer 302 andthe third metal layer 301 at the bottom thereof.

In a similar manner, in a multi-color light emitting pixel unitincluding first to Mth types of LEDs in another embodiment of thepresent disclosure, the Mth type of LED has M light emitting layers anda metal layer is arranged at the bottom of each light emitting layer,wherein M is positive integer and greater than or equal to number two.In each one of the first to Mth type of LEDs, a top conductive layer (asan upper conductive layer) is arranged at the top of a top lightemitting layer, so that the micro-gap structure in the top lightemitting layer can be isolated and sealed between the top conductivelayer and the metal layer at the bottom of the top light emitting layer.The micro-gap structure in every light emitting layer is isolated andsealed between the metal layers separately at the top and bottom of therelative light emitting layer.

In addition, similar to the multi-color light emitting pixel units 1000to 4000 in FIGS. 1 to 4, a multi-color light emitting pixel unitaccording to another embodiment of the present disclosure includes aplurality of LEDs, including a first type of LED to a Mth type of LED.The Mth type of LED includes, at least, all of the light emitting layersand metals layers constructed in the (M−1)th type of LED, and an Mthlight emitting layer and an Mth metal layer. On the basis thereof, theMth type of LED has an (M−1)th electrical connector which connects tothe Mth metal layer, the (M−1)th metal layer, . . . , and the firstmetal layer. Furthermore, the (M−1)th electrical connector can connectto the Mth metal layer, the (M−1)th type of light emitting layer, the(M−1)th metal layer, . . . , the first type of light emitting layer, andthe first metal layer. The arrangement of the (M−1)th electricalconnector can be referred to the description of the first electricalconnector 203 in the FIG. 1. The first to the (M−1)th electricalconnectors connect the first to Mth metal layers, and the first to the(M−1)th electrical connectors can directly contact the substrate and thefirst metal layer. Herein, there is a difference from the first type ofLED to the Mth type of LED. Additionally, every kind of LED can beselected from one of the red LED, green LED, blue LED, yellow LED,orange LED, purple LED or cyan LED. Herein, the different color LEDs areconventional LEDs, which can be known by those skilled in the art andwill not be described herein. Furthermore, the first type of LED to theMth type of LED are spaced apart on the same substrate. A top isolationlayer covers the exposed surface of the substrate and that of the firstto Mth types of LEDs. The top isolation layer of every type of LED hasan opening thereof and a transparent conductive layer covers the surfaceof the top isolation layer and is filled in the opening, wherein thetransparent conductive layer at the bottom of the opening electricallycontacts the top light emitting layer of every type of LED. Referring toFIGS. 4 and 5, in the pixel unit having M types of LEDs, the size of thelight emitting areas of the first to Mth types of LEDs are differentfrom each other. According to the arrangement of the LEDs in the pixelunit, the size of the light emitting area of the first type of LED islarger than those of the other types of LEDs. Optionally, the first typeof LED is a red LED which has the larger light emitting area than thoseof the other types of LEDs. Alternatively, the other types of LEDs atleast include a green LED or a blue LED.

A multi-color micro-display panel is also provided according to anembodiment of the present disclosure. The micro-display panel includes aplurality of multi-color pixel units which are arranged in a matrix. Themulti-color pixel units herein can be the LED pixel units mentionedabove.

Hereafter combined with the drawings, the method of fabricating themulti-color light emitting pixel unit will be further described below.

FIG. 6 is a flow chart illustrating a the method of fabricating themulti-color light emitting pixel unit shown in FIG. 1, according to anembodiment of the present disclosure. FIGS. 7 to 10 are cross-sectionalviews illustrating structures formed in the steps illustrated in FIG. 6,according to an embodiment of the present disclosure. Referring to FIG.6, the method of fabricating the multi-color light emitting pixel unitas shown in FIG. 1 includes the following steps.

In step S601, referring to FIG. 7, a stack structure including a firstmetal layer 101, a first type of light emitting layer 102, a secondmetal layer 201, and a second type of light emitting layer 202, areformed on a substrate 100 from bottom to top. In other words, the firsttype of light emitting layer 102 and the second type of light emittinglayer 202 are stacked on the substrate 100 from bottom to top. The firstmetal layer 101 is formed at the bottom of the first type of lightemitting layer 102. The second metal layer 201 is formed at the bottomof the second type of light emitting layer 202. The second metal layer201 is arranged between the first type of light emitting layer 102 andthe second light emitting layer 202.

More specifically, the substrate 100 can be, but not limited to, an ICsubstrate.

FIG. 11 is a flow chart illustrating the details of step S601 in FIG. 6,according to an embodiment of the disclosure. FIGS. 12 to 21 arecross-sectional views illustrating structures formed in the stepsillustrated FIG. 11, according to an embodiment of the presentdisclosure. Referring to FIG. 11, step S601 further includes thefollowing specific steps.

In step S101, referring to FIG. 12, a first metal bonding layer M01 isformed on the substrate 100, the first type of light emitting layer 102is formed on a first base B1, and a second metal bonding layer M02 isformed on top of the first type of light emitting layer 102.

More specifically, the first metal bonding layer M01 can be prepared by,but not limited to, physical vapor deposition, such as evaporation,sputtering, etc. The material of the first base B1 is designed accordingto the first type of light emitting layer 102. For example, the firstbase B1 can be a gallium nitride (GaN) base. The first type of lightemitting layer 102 can be formed by, but not limited to, epitaxialgrowth on the first base B1. The second metal bonding layer M02 can beprepared by, but not limited to, physical vapor deposition, such asevaporation.

In step S102, referring to FIG. 13 combined with FIG. 12, the first baseB1 is turned upside down so that the second metal bonding layer M02faces the first metal bonding layer M01, and then the second metalbonding layer M02 is bonded with the first metal bonding layer M01 toform the first metal layer 101.

In step S103, referring to FIG. 14 combined with FIG. 13, the first baseB1 is removed.

Herein, after the first base B1 is removed, referring to FIG. 15, thestep S103 can further includes: thinning the first type of lightemitting layer 102.

In addition, according to an embodiment, after the first base B1 isremoved or the first type of light emitting layer 102 is thinned, andbefore the third metal bonding layer is formed, referring to FIG. 16,step S103 can further include: forming micro-gap structures 06 in thefirst type of light emitting layer 102. The micro-gap structures 06 areformed by, but not limited to, photolithography and etching. Inphotolithography, a lithography pattern is designed according to thedimension of the micro-gap structure 06. According to an embodiment, across-sectional dimension of the micro-gap structure pattern is not morethan 2 nm. Here, the cross-sectional dimension of the air gap can be thediameter of the cross section of the air gap, or the length or width ofthe cross section of the air gap.

In step S104, referring to FIG. 17, a third metal bonding layer M03 isformed on the first type of light emitting layer 102, the second type oflight emitting layer 202 is formed on a second base B2, and a fourthmetal bonding layer M04 is formed on top of the second type of lightemitting layer 202.

In step S105, referring to FIG. 18 combined with FIG. 17, the secondbase B2 is turned upside down, so that the fourth metal bonding layerM04 faces the third metal bonding layer M03, and bonding the fourthmetal bonding layer M04 with the third metal bonding layer M03 to formthe second metal layer 201.

In step S106, referring to FIG. 19 combined with FIG. 18, the secondbase B2 is removed.

Herein, after the second base B2 is removed, referring to FIG. 20, instep S106, the second type of light emitting layer 202 is thinned.

According to an embodiment, after the second base B2 is removed or thesecond type of light emitting layer 202 is thinned, referring to FIG.21, in the step S106, micro-gap structures 06 are formed in the secondtype of light emitting layer 202. The micro-gap structures 06 are formedusing a process similar to the process of forming the micro-gapstructure 06 in the first type of light emitting layer 102. Therefore,descriptions of the process of forming the micro-gap structures 06 inthe second type of light emitting layer 202 will not be repeated.

Referring back to FIGS. 6-10, the process after step S601 according tothe embodiment of the present disclosure will be further describedhereafter.

In step S602, referring to FIG. 8, the second type of light emittinglayer 202 and the second metal layer 201 are patterned until a portionof the top of the first type of light emitting layer 102 is exposed,thereby forming a step structure made by the second type of lightemitting layer 202 on the first type of light emitting layer 102.

More specifically, the process of patterning the second type of lightemitting layer 202 and the second metal layer 201 can be performed byphotolithography and plasma etching. The process of patterning thesecond type of light emitting layer 202 and the second metal layer 201also includes: over etching the top of the first type of light emittinglayer 102. The parameters of the patterning process can be set accordingto actual needs, which will not be limited herein.

In step S603, referring to FIG. 9, according to a pre-set first type oflight emitting region A01 and a pre-set second type of light emittingregion A02, the second type of light emitting layer 202, the secondmetal layer 201, the first type of light emitting layer 102, and thefirst metal layer 101 are etched, so as to segment the first type oflight emitting layer 102 in the first type of light emitting region A01from the first type of light emitting layer 102 in the second type oflight emitting region A02, and to segment the first metal layer 101 inthe first type of light emitting region A01 from the first metal layer101 in the second type of light emitting region A02. As a result of stepS603, a first type of LED 01 including a first segment of the firstmetal layer 101-1 and a first segment of the first type of lightemitting layer 102-1, and a second type of LED 02 including a secondsegment of the first metal layer 101-2, a second segment of the firsttype of light emitting layer 102-2, a first segment of the second metallayer 201-1, and a second segment of the second type of light emittinglayer 202-1 are formed.

Herein, the process of etching the second type of light emitting layer202, the second metal layer 201, the first type of light emitting layer102, and the first metal layer 101 is performed by photolithography andetching. The parameters of the process of etching can be set accordingto the actual needs.

According to an embodiment, as a result of step S603, a plurality ofmulti-color light emitting pixel units are segmented from each otheraccording to a pre-set pixel unit array. In this manner, the lightemitting transistors in a pixel unit and/or in an array of pixel unitscan be prepared by one segmenting step, which simplifies the process anddecreases the production cost, especially facilitates the large-scaleproduction.

In step S604, referring to FIG. 10, a shared top electrode layer 05,which functions as an extraction electrode of the second metal layer201, is formed on the tops of the first segment of the first type oflight emitting layer 102-1 and the first segment of the second type ofthe light emitting layer 202-1 in the second type of light emittingregion A02.

FIG. 22 is a flow chart illustrating the details of step S604 in FIG. 6,according to an embodiment of the present disclosure. FIGS. 23 to 25 arecross-sectional views illustrating structures formed in the stepsillustrated FIG. 22, according to an embodiment of the presentdisclosure. Referring to FIG. 22, the specific process of the step S604includes the following steps.

In step S401, referring to FIG. 23, part of the first segment of thesecond type of light emitting layer 202-1 is removed, so as to exposepart of the first segment of the second metal layer 201-1.

In step S402, referring to FIG. 24, the first electrical connector 203is formed on the side wall and the top of the first segment of thesecond metal layer 201-1, the sidewall of the second segment of thefirst type of light emitting layer 102-2, and the sidewall of the secondsegment of the first metal layer 101-2 in the second type of lightemitting region A02.

FIGS. 26 to 27 are cross-sectional views illustrating structures formedin the step of fabricating the first electrical connector 203, accordingto an embodiment of the present disclosure. In step S402, the firstelectrical connector 203 is formed by the following specific steps.

In step S4021, referring to FIG. 26 combined with FIG. 24, a mask Y isformed to shield the region without the first electrical connector 203,thereby exposing the top and the sidewall of the first segment of thesecond metal layer 201-1, the sidewall of the second segment of thefirst type of light emitting layer 102-2, and the sidewall of the secondsegment of the first metal layer 101-2 in the second type of lightemitting region A02.

In step S4022, referring to FIG. 27, a conductive material 203′ isdeposited on the substrate 100 after completing the step S4021.

In step S4023, referring to FIG. 10 again, the mask Y and the conductivematerial 203′ on the mask Y are removed, so as to form the firstelectrical connector 203 on the top and the sidewall of the firstsegment of the second metal layer 201-1, the sidewall of the secondsegment of the first type of light emitting layer 102-2, and thesidewall of the second segment of the first metal layer 101-2 in thesecond type of light emitting region A02.

The process of fabricating the shared top electrode layer 05 will befurther described hereinafter.

In step S403, referring to FIG. 25, an isolation layer 04 is formed tocover the first type of light emitting region A01, the second type oflight emitting region A02, and the surface of the exposed substrate 100.The isolation layer 04 has openings on the first segment of the firsttype of light emitting layer 102-1 in the first type of light emittingregion A01 and the first segment of the second type of light emittinglayer 202-1 in the second type of light emitting region A02.

In step S404, referring to FIG. 10 again, the continuous shared topelectrode layer 05 is formed on the whole substrate 100 after step S403,by, for example, deposition. The shared top electrode layer 05 formed inthe openings is connected to the first segment of the first type oflight emitting layer 102-1 in the first type of light emitting regionA01 and the first segment of the second type of light emitting layer202-1 in the second type of light emitting region A02.

FIG. 28 illustrates the structure of the multi-color light emittingpixel unit having micro-gap structures in the first type of lightemitting layer 102 and the second type of light emitting layer 202,according to an embodiment of the present disclosure.

FIG. 29 is a flow chart illustrating a method of fabricating themulti-color light emitting pixel unit 3000 as shown in FIG. 3, accordingto an embodiment of the present disclosure. FIGS. 30 to 34 arecross-sectional views illustrating structures formed in the stepsillustrated in FIG. 6, according to an embodiment of the presentdisclosure. Referring to FIG. 29, the method of fabricating themulti-color light emitting pixel unit 3000 as shown in FIG. 3 includesthe following steps.

In step S701, referring to FIG. 30, a stack structure including a firstmetal layer 101, a first type of light emitting layer 102, a secondmetal layer 201, a second type of light emitting layer 202, a thirdmetal layer 301, and a third type of light emitting layer 302 is formedon a substrate 100 in an order from bottom to top. In other words, thefirst type of light emitting layer 102, the second type of lightemitting layer 202, and the third type of light emitting layer 302 arestacked on the substrate 100 from bottom to top. The first metal layer101 is formed at the bottom of the first type of light emitting layer102. The second metal layer 201 is formed at the bottom of the secondtype of light emitting layer 202. The third metal layer 301 is formed atthe bottom of the third type of light emitting layer 302. The secondmetal layer 201 is arranged between the first type of light emittinglayer 102 and the second type of light emitting layer 202. The thirdmetal layer 301 is arranged between the second type of light emittinglayer 202 and the third type of light emitting layer 302.

FIG. 35 is a flow chart illustrating the details of step S701 in FIG.29, according to an embodiment of the disclosure. Referring to FIG. 35combined with FIG. 30, step S701 further includes the following steps.It is noted that, the structures formed in the steps S801 to S809 of thepresent embodiment are not shown in drawings. But the steps S801 to S809of the present embodiment can be understood by those of skill in the artwith reference to the steps S101 to S109 of the embodiment describedabove.

In step S801, a first metal bonding layer is formed on the substrate100, the first type of light emitting layer 102 is formed on a firstbase, and a second metal bonding layer is formed on the top of the firsttype of light emitting layer 102.

More specifically, the first metal bonding layer can be prepared by, butnot limited to, physical vapor deposition, such as evaporation,sputtering, etc. The material of the first base is designed according tothe first type of light emitting layer 10. For example, the first basecan be a gallium nitride (GaN) base. The first type of light emittinglayer 102 can be made by, but not limited to, epitaxial growth on thefirst base. The second metal bonding layer can be prepared by, but notlimited to, physical vapor deposition, such as evaporation.

In step S802, the first base is turned upside down so that the secondmetal bonding layer faces the first metal bonding layer, and the secondmetal bonding layer is bonded with the first metal bonding layer to formthe first metal layer 101.

In step S803, the first base is removed.

Herein, after the first base is removed, step S803 can further include:thinning the first type of light emitting layer 102. In addition, afterthe first base is removed or the first type of light emitting layer 102is thinned, and before the third metal bonding layer is formed,referring to FIG. 36, step S803 can further include: forming micro-gapstructures 06 in the first type of light emitting layer 102. Themicro-gap structures 06 are formed by, but not limited to,photolithography and etching. In photolithography, a lithography patternis designed according to the dimension of the micro-gap structure 06.According to an embodiment, a cross-sectional dimension of the micro-gapstructure pattern is not more than 2 nm.

In step S804, a third metal bonding layer is formed on the first type oflight emitting layer 102, the second type of light emitting layer 202 isformed on a second base, and a fourth metal bonding layer is formed onthe top of the second type of light emitting layer 202.

In step S805, the second base is turned upside down so that the fourthmetal bonding layer faces the third metal bonding layer and then thefourth metal bonding layer is bonded with the third metal bonding layerto form the second metal layer 201.

In step S806, the second base is removed.

Herein, after the second base is removed, step S106 can further include:thinning the second type of light emitting layer 202. In addition, afterthe second base is removed or the second type of light emitting layer202 is thinned, referring to FIG. 36, the step S106 further includes:forming micro-gap structures 06 in the second type of light emittinglayer 202. The micro-gap structure 06 can be formed using a processsimilar to the process of forming the micro-gap structure 06 describedabove. Therefore, description of the process of forming the micro-gapstructure 06 will not be repeated.

In step S807, a fifth metal bonding layer is formed on the second typeof light emitting layer 202, the third type of light emitting layer 302is formed on a third base, and a sixth metal bonding layer is formed ontop of the third type of light emitting layer 302.

In step S808, the third base is turned upside down so that the sixthmetal bonding layer faces the fifth metal bonding layer and then thesixth metal bonding layer is bonded with the fifth metal bonding layerto form the third metal layer 301.

In step S809, the third base is removed.

Herein, after the third base is removed, step S109 can further include:thinning the third type of light emitting layer 302. In addition, afterthe third base is removed or the third type of light emitting layer 302is thinned, referring to FIG. 36, the step S109 further includes:forming micro-gap structures 06 in the third type of light emittinglayer 302. The micro-gap structure 06 can be formed using a processsimilar to the process of forming the micro-gap structure 06 describedabove. Therefore, description of the process of forming the micro-gapstructure 06 will not be repeated.

FIG. 36 illustrates the micro-gap structures 06 in the first type oflight emitting layer 102, the second type of light emitting layer 202,and the third type of light emitting layer 302.

Referring back to FIGS. 30-34, the process after step S701 will befurther described hereafter.

In step S702, referring to FIG. 31, the third type of light emittinglayer 302 and the third metal layer 301 are patterned until a portion ofthe top of the second type of light emitting layer 202 is exposed,thereby forming a step structure made by the third type of lightemitting layer 302 on the second type of light emitting layer 202.

More specifically, the step structure includes the third type of lightemitting layer 302 and the third metal layer 301. The process ofpatterning the third type of light emitting layer 302 and the thirdmetal layer 301 also includes: over etching the top of the first type oflight emitting layer 102.

In step S703, referring to FIG. 32, the second type of light emittinglayer 202 and the second metal layer 201 are further patterned until aportion of the top of the first type of light emitting layer 202 isexposed, thereby forming a step structure made by the second type oflight emitting layer 202 on the first type of light emitting layer 102.

More specifically, the step structure is made by the second type oflight emitting layer 202 and the second metal layer 201. The patterningprocess can be performed by photolithography and plasma etching. Theprocess of patterning the second type of light emitting layer 202 andthe second metal layer 201 also includes: over etching the top of thefirst type of light emitting layer 102. The parameters of the patterningprocess can be set according to the actual needs, which will not belimited herein.

In step S704, referring to FIG. 33, according to a pre-set first type oflight emitting region A01, a pre-set second type of light emittingregion A02, and a pre-set third type of light emitting region A03, thethird type of light emitting layer 302, the third metal layer 301, thesecond type of light emitting layer 202, the second metal layer 201, thefirst type of light emitting layer 102, and the first metal layer 101are etched, so as to segment the first type of light emitting layer 102in the first type of light emitting region A01 from that in the secondtype of light emitting region A02 and from that in the third type oflight emitting region A03, segment the first metal layer 101 in thefirst type of light emitting region A01 from that in the second type oflight emitting region A02 and from that in the third type of lightemitting region A03, segment the second type of light emitting layer 202in the second type of light emitting region A02 from that in the thirdtype of light emitting region A03, and segment the second metal layer201 in the second type of light emitting region A02 from that in thethird type of light emitting region A03. As a result of step S704, afirst type of LED 01 including a first segment of the first metal layer101-1 and a first segment of the first type of light emitting layer102-1, a second type of LED 02 including a second segment of the firstmetal layer 101-2, a second segment of the first type of light emittinglayer 102-2, a first segment of the second metal layer 201-1, and afirst segment of the second type of light emitting layer 202-1, and athird type of LED 03 including a third segment of the first metal layer101-3, a third segment of the first type of light emitting layer 102-3,a second segment of the second metal layer 201-2, a second segment ofthe second type of light emitting layer 202-2, a first segment of thethird metal layer 301-1, and a first segment of the third type of lightemitting layer 302-1, are formed.

Herein, the etching process is performed by photolithography and etchingprocess, the parameters of which can be set according to the actualneeds.

According to an embodiment, as a result of step S704, a plurality ofmulti-color light emitting pixel units are segmented from each otheraccording to a pre-set pixel unit array. Therefore, the light emittingtransistors in a pixel unit and/or in an array of pixel units can beprepared by one segmenting step, which simplifies the process anddecreases the production cost, especially facilitates the large-scaleproduction.

In step S705, referring to FIG. 34, a shared top electrode layer 05,which functions as an extraction electrode of the first segment of thesecond metal layer 201-1 and an extraction electrode of the firstsegment of the third metal layer 301-1 is formed on the top of the firstsegment of the first type of light emitting layer 102-1, the firstsegment of the second type of light emitting layer 202-1, and the firstsegment in the third type of light emitting layer 302-1.

FIG. 37 is a flow chart illustrating the details of step S705 in FIG.29, according to an embodiment of the present disclosure. FIGS. 38 to 40are cross-sectional views illustrating structures formed in the stepsillustrated in FIG. 37. Referring to FIG. 37, step S705 further includesthe following steps.

In step S501, referring to FIG. 38, part of the first segment of thethird type of light emitting layer 302-1 and part of the first segmentof the second type of light emitting layer 202-1 are removed, so as toexpose part of the first segment of second metal layer 201-1 and part ofthe first segment of the third metal layer 301-1.

In step S502, referring to FIG. 39, the first electrical connector 203is formed on the side wall and the top of the first segment of thesecond metal layer 201-1, the sidewall of the second segment of thefirst type of light emitting layer 102-2, and the sidewall of the secondsegment of the first metal layer 101-2 in the second type of lightemitting region A02, and a second electrical connector 303 is formed onthe top and the sidewall of the first segment of the third metal layer301-1, the sidewall of the second segment of the second type of lightemitting layer 202-2, the sidewall of the second segment of the secondmetal layer 201-2, the sidewall of the third segment of the first typeof light emitting layer 102-3, and the sidewall of the third segment ofthe first metal layer 101-3 in the third type of light emitting regionA03.

More specifically, referring to FIG. 39, the process of fabricating thefirst electrical connector 203 and the second electrical connector 303further includes the following steps. It is noted that, the followingsteps S5021 to S5023 are not shown in drawings, but steps S5021 to S5023can be understood by those of skill in the art with reference to stepsS4021 to S4023 of the embodiment described above.

In step S5021, a mask is formed on the substrate 100 to shield theregion without the first electrical connector 203, and the secondelectrical connector 303, thereby exposing the top and the sidewall ofthe first segment of the second metal layer 201-1, the sidewall of thesecond segment of the first type of light emitting layer 102-2, and thesidewall of the second segment of the first metal layer 101-2 in thesecond type of light emitting region A02, and exposing the top and thesidewall of the first segment of the third metal layer 301-1, thesidewall of the second segment of the second type of light emittinglayer 202-2, the sidewall of the second segment of the second metallayer 201-2, the sidewall of the third segment of the first type oflight emitting layer 102-3, and the sidewall of the third segment of thefirst metal layer 101-3 in the third type of light emitting region A03.

In step S5022, a conductive material is deposited on the substrate 100after completing the step S5021.

In step S5023, referring to FIG. 39, the mask and the conductivematerial on the mask are removed, so as to form the first electricalconnector 203 on the top and the sidewall of first segment of the secondmetal layer 201-1, the sidewall of the second segment of the first typeof light emitting layer 102-2, and the sidewall of the second segment ofthe first metal layer 101-2 in the second type of light emitting regionA02, and form the second electrical connector 303 on the top and thesidewall of the first segment of the third metal layer 301-1, thesidewall of the second segment of the second type of light emittinglayer 202-2, the sidewall of the second segment of the second metallayer 201-2, the sidewall of the third segment of the first type oflight emitting layer 102-3, and the sidewall of the third segment of thefirst metal layer 101-3 in the third type of light emitting region A03.

The process of fabricating the shared top electrode layer 05 will befurther described hereinafter.

In step S503, referring to FIG. 40, an isolation layer 04 is formed tocover the first type of light emitting region A01, the second type oflight emitting region A02, the third type of light emitting region A03,and the surface of the exposed substrate 100. The isolation layer 04 hasopenings on the first segment of the first type of light emitting layer102-1, on the first segment of the second type of light emitting layer202-1, and on the first segment of the third type of light emittinglayer 302-1.

In step S504, referring to FIG. 34 again, the continuous shared topelectrode layer 05 is formed on the entire substrate 100 after stepS503. The shared top electrode layer 05 deposited in the openings isconnected to the first segment of the first type of light emitting layer102-1, to the first segment of the second type of light emitting layer202-1, and to the first segment of the third type of light emittinglayer 302.

As mentioned above, in the method of fabricating the multi-color lightemitting pixel unit according to the embodiments of the presentdisclosure, because the films deposition processes in every type of LEDcan be performed simultaneously, the LED can be prepared at the sametime without being separately prepared, thereby simplifying theprocesses of fabricating the multi-color light emitting pixel unit andthe micro-LED display panel and facilitating large-scale production. Asa result of the fabrication method according to the embodiments of thepresent disclosure, different types of LEDs are arranged side by side ona same substrate with a short distance between each other. Therefore,the size of the LEDs and the display panel made of the LEDs can bereduced. For example, the size of each LED can be 40 μm×40 μm. Inaddition, the tops of the different types of LEDs are not at the samehorizontal plane. That is to say, the heights of the different types ofLEDs are not the same, so as to expose the different types of lightemitting layers on the top of different types of LEDs, thus ensuring thelight emitting area and improving emission efficiency of every LED, andimproving the integration of various LEDs. A micro-LED display panelformed by the pixel units of the embodiments of the present disclosurehas a clear picture display and high resolution. Furthermore, since theelectrical connector connects every metal layer in the Mth type of LED,the Mth type of light emitting layer, which is the top light emittinglayer, in the Mth type of LED can emit light while the other lightemitting layers in the Mth type of LED are short-circuited because themetal layers disposed on both sides of each one of the other lightemitting layers are electrically connected to each other. For example,in the Mth type of LED, the first type of light emitting layer isshort-circuited because the first type of metal layer and the secondtype of metal layer disposed on both sides of the first type of lightemitting layer are electrically connected with each other; the secondtype of light emitting layer is short-circuited because the second typeof metal layer and the third type of metal layer disposed on both sidesof the second type of light emitting layer are electrically connectedwith each other; and so on. Therefore, various types of LEDs emit lightseparately without affecting each other. Furthermore, the micro-gap inthe light emitting layer can release the stress in the interior of thelight emitting layer and avoid warping thereof without influence on thelight emitting efficiency of the light emitting layer, so as to improvethe product yield.

While the invention has been particularly shown and described withreferences to preferred embodiments thereof, if will be understood bythose skilled in the art that various changes in form and details may bemade herein without departing from the spirit and scope of the inventionas defined by the appended claims.

The invention claimed is:
 1. A method for fabricating a multi-colorlight emitting pixel unit, comprising: forming a stack structure on asubstrate, the stack structure comprising a first metal layer, a firsttype of light emitting layer, a second metal layer, and a second type oflight emitting layer in an order from bottom to top; patterning thesecond type of light emitting layer and the second metal layer until aportion of a top surface of the first type of light emitting layer isexposed; and selectively etching the stack structure to expose a sidesurface of the first metal layer to form a first light emittingtransistor and a second light emitting transistor, the first lightemitting transistor including the first metal layer and the first typeof light emitting layer, and the second light emitting transistorincluding the first metal layer, the first type of light emitting layer,the second metal layer, and the second type of light emitting layer. 2.The method of claim 1, wherein the forming the stack structure on thesubstrate comprises: forming the first metal layer and the first type oflight emitting layer on the substrate from bottom to top of thesubstrate; forming a first metal bonding layer on top of the first typeof light emitting layer; forming the second type of light emitting layerand a second metal bonding layer on a first base from bottom to top ofthe first base; bonding the first metal bonding layer and the secondmetal bonding layer to form the second metal layer; and removing thefirst base.
 3. The method of claim 2, wherein the forming the firstmetal layer and the first type of light emitting layer on the substratefrom bottom to top of the substrate comprises: forming a third metalbonding layer on the substrate; forming the first type of light emittinglayer and a fourth metal bonding layer on a second base from bottom totop of the first base; bonding the third metal bonding layer and thefourth metal bonding layer to form the first metal layer; and removingthe second base.
 4. The method of claim 2, further comprising: beforeforming the first metal bonding layer on top of the first type of lightemitting layer, thinning the first type of light emitting layer.
 5. Themethod of claim 2, further comprising: thinning the second type of lightemitting layer.
 6. The method of claim 2, further comprising: formingmicro-gap structures in at least one of the first type of light emittinglayer or the second type of light emitting layer.
 7. The method of claim2, further comprising: forming micro-gap structures in both of the firsttype of light emitting layer and the second type of light emittinglayer, wherein the micro-gap structures in the first type of lightemitting layer are staggered relative to the micro-gap structures in thesecond type of light emitting layer.
 8. The method of claim 1, furthercomprising: electrically connecting the first metal layer and the secondmetal layer in the second light emitting transistor.
 9. The method ofclaim 8, wherein the electrically connecting the first metal layer andthe second metal layer in the second light emitting transistorcomprises: removing a portion of the second type of light emitting layerin the second light emitting transistor, so as to expose a top portionof the second metal layer in the second light emitting transistor; andforming an electrical connector on the exposed top portion and a sidewall of the second metal layer in the second light emitting transistor,and on side walls of the first type of light emitting layer and thefirst metal layer in the second light emitting transistor.
 10. Themethod of claim 1, further comprising: forming a top electrode layer ontop of the first light emitting transistor and the second light emittingtransistor.
 11. The method of claim 10, wherein the forming the topelectrode layer on top of the first light emitting transistor and thesecond light emitting transistor comprises: forming an isolation layercovering the first light emitting transistor and the second lightemitting transistor; forming a first opening and a second opening in theisolation layer, the first opening exposing a portion of the first typeof light emitting layer in the first light emitting transistor, and thesecond opening exposing a portion of the second type of light emittinglayer in the second light emitting transistor; and forming the topelectrode layer on the substrate, the top electrode layer contacting thefirst type of light emitting layer in the first light emittingtransistor via the first opening and contacting the second type of lightemitting layer in the second light emitting transistor via the secondopening.
 12. The method of claim 1, wherein the stack structure furthercomprises a third metal layer formed on top of the second type of lightemitting layer, and a third type of light emitting layer formed on topof the third metal layer, the method further comprising patterning thethird type of light emitting layer and the third metal layer until aportion of the second type of light emitting layer is exposed, and theselectively etching the stack structure further comprising selectivelyetching the stack structure to form the first light emitting transistor,the second light emitting transistor, and a third light emittingtransistor, the third light emitting transistor including the firstmetal layer, the first type of light emitting layer, the second metallayer, the second type of light emitting layer, the third metal layer,and the third type of light emitting layer.
 13. The method of claim 12,wherein the forming the stack structure on the substrate comprises:forming the first metal layer, the first type of light emitting layer,the second metal layer, the second type of light emitting layer on thesubstrate from bottom to top; forming a first metal bonding layer on thesecond type of light emitting layer; forming the third type of lightemitting layer and a second metal bonding layer on a base from bottom totop of the base; bonding the first metal bonding layer and the secondmetal layer to form the third metal layer; and removing the base. 14.The method of claim 12, further comprising: thinning at least one of thefirst type of light emitting layer, the second type of light emittinglayer, or the third type of light emitting layer.
 15. The method ofclaim 12, further comprising: forming micro-gap structures in at leastone of the first type of light emitting layer, the second type of lightemitting layer, or the third type of light emitting layer.
 16. Themethod of claim 12, further comprising: forming micro-gap structures inall of the first type of light emitting layer, the second type of lightemitting layer, and the third type of light emitting layer, wherein themicro-gap structures in the first type of light emitting layer arestaggered relative to the micro-gap structures in the second type oflight emitting layer, and wherein the micro-gap structures in the secondtype of light emitting layer are staggered relative to the micro-gapstructures in the third type of light emitting layer.
 17. The method ofclaim 12, further comprising: electrically connecting the first metallayer and the second metal layer in the second light emittingtransistor, and electrically connecting the first metal layer, thesecond metal layer, and the third metal layer in the third lightemitting transistor.
 18. The method of claim 17, wherein theelectrically connecting the first metal layer and the second metal layerin the second light emitting transistor, and electrically connecting thefirst metal layer, the second metal layer, and the third metal layer inthe third light emitting transistor comprises: removing a portion of thesecond type of light emitting layer in the second light emittingtransistor, so as to expose a top portion of the second metal layer inthe second light emitting transistor; removing a portion of the thirdtype of light emitting layer in the third light emitting transistor, soas to expose a top portion of the third metal layer in the third lightemitting transistor; forming a first electrical connector on the exposedtop and a side wall of the second metal layer in the second lightemitting transistor, and on side walls of the first type of lightemitting layer and the first metal layer in the second light emittingtransistor; and forming a second electrical connector on the exposed topand a side wall of the third metal layer in the third light emittingtransistor, and on side walls of the second type of light emittinglayer, the second metal layer, the first type of light emitting layer,and the first metal layer in the third light emitting transistor. 19.The method of claim 12, further comprising: forming a top electrodelayer on top of the first light emitting transistor, the second lightemitting transistor, and the third light emitting transistor.
 20. Themethod of claim 19, wherein the forming a top electrode layer on top ofthe first light emitting transistor, the second light emittingtransistor, and the third light emitting transistor comprises: formingan isolation layer covering the first light emitting transistor, thesecond light emitting transistor, and the third light emittingtransistor; forming a first opening, a second opening, and a thirdopening in the isolation layer, the first opening exposing a portion ofthe first type of light emitting layer in the first light emittingtransistor, the second opening exposing a portion of the second type oflight emitting layer in the second light emitting transistor, and thethird opening exposing a portion of the third type of light emittinglayer in the third light emitting transistor; and forming the topelectrode layer on the substrate, the top electrode layer contacting thefirst type of light emitting layer in the first light emittingtransistor via the first opening, contacting the second type of lightemitting layer in the second light emitting transistor via the secondopening, and contacting the third type of light emitting layer in thethird light emitting transistor via the third opening.